[libata] kill ata_sg_is_last()

Short term, this works around a bug introduced by early sg-chaining
work.

Long term, removing this function eliminates a branch from a hot
path loop in each scatter/gather table build.  Also, as this code
demonstrates, we don't need to _track_ the end of the s/g list, as
long as we mark it in some way.  And doing so programatically is nice.
So its a useful cleanup, regardless of its short term effects.

Based conceptually on a quick patch by Jens Axboe.

Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
This commit is contained in:
Jeff Garzik
2007-10-18 16:21:18 -04:00
parent 858c9c4066
commit 3be6cbd73f
5 changed files with 27 additions and 42 deletions

View File

@@ -5134,6 +5134,7 @@ static void ipr_build_ata_ioadl(struct ipr_cmnd *ipr_cmd,
u32 ioadl_flags = 0;
struct ipr_ioarcb *ioarcb = &ipr_cmd->ioarcb;
struct ipr_ioadl_desc *ioadl = ipr_cmd->ioadl;
struct ipr_ioadl_desc *last_ioadl = NULL;
int len = qc->nbytes + qc->pad_len;
struct scatterlist *sg;
@@ -5156,11 +5157,13 @@ static void ipr_build_ata_ioadl(struct ipr_cmnd *ipr_cmd,
ata_for_each_sg(sg, qc) {
ioadl->flags_and_data_len = cpu_to_be32(ioadl_flags | sg_dma_len(sg));
ioadl->address = cpu_to_be32(sg_dma_address(sg));
if (ata_sg_is_last(sg, qc))
ioadl->flags_and_data_len |= cpu_to_be32(IPR_IOADL_FLAGS_LAST);
else
ioadl++;
last_ioadl = ioadl;
ioadl++;
}
if (likely(last_ioadl))
last_ioadl->flags_and_data_len |= cpu_to_be32(IPR_IOADL_FLAGS_LAST);
}
/**